Just wondering what plugs people run

Atm i Got NGK ones, BP6EY? i think
Engine is a 1.8L stock, with extractors and 2" exhaust

Checking the plugs against the guide in the Haynes manual it says my Plug is Overheating due to either Low Octane Fuel, Ignition timing, or weak fuel mixture. Tip is a Light brown colour, and some of the white bit in center is light brown and white.

Carby is a stock 1.6L one and ran fine on the 1.6L. is going to a 1.8L making it run lean? going to double check timing when i get hold of a light, and will fill up with a fresh tank of Unleaded. (surely it wouldn't need premium?)

Any tips be great